Navien Tankless and Hot Water Circulator

I am trying to educate myself a bit on some work we are doing at our home and I need to make sure I ask for the right bid.

All.. I have a scenario that I need some opinions on.

Our wish list

We are looking to replace our existing hot water storage heater with the most energy efficient tankless solution that we can, yet still be practical with the cost of putting it into service. We live an an area in which our ground water is approx 45 degrees and we sleep with the house at 60 degrees at night. We would also like to stop wasting 2 - 3 minutes of water (approx 6 gallons of water) every morning that we shower while we wait for the hot water to arrive. We don't mind pushing a button (or something similar) and waiting 20 - 30 seconds for the hot water to arrive at the faucet - we just do not want it to go down the drain. We want to make sure that we aren't using the existing water lines as a mini storage tank - which would defeat the purpose of efficiencies. We also do not want water from the hot water line to be puleed into the cold water line when the cold water is turned on. Our home is approximately 3200 square feet and is finished and we don't have a dedicated recirculation line. I am making an assumption that it will be expensive to retrofit a dedicated recirculation line into our home.

Potential Solution

For the tankless solution we are looking at a Navien (NR210, NR210A, NR240 and NR240A) - I think we'll need the NR240/NR240A unit because of the 75-80 degree temperature rise that we'll need during the cold months. To help with the waste of water we are looking at a Taco D'Mand, RedyTemp, or ACT Metlund D'Mand.

Questions

With the wishes that that we have will the potential solutions suffice?
With the circulators listed should you go with one of the Navien 'A' units or not?
Is there anything else that I should be considering to meet our wishes?

In advance I appreicate your feedback as it will help me intelligently choose the right contractor for my job.

Without a dedicated return line, the only one that lets you adjust the amount of warm water that goes into the cold line used as the return, is the RedyTemp. All of the others can't be adjusted, or at least easily in their cutoff point.

Depends on how your house is layed out how easy it would be to add a recirculation system. Most of them can be setup to to only come on upon user initiation.

My guess is that if used in this demand mode, rather than a continuous or timer based use, the thing wouldn't impact the tankless' operational life - it would just look like a longer demand cycle.

I have a RedyTemp unit hooked up so it only brings the water at the vanity to barely warm. The shower tap off that line is closer to the WH. So, after flushing the toilet, it has purged all of the warm water out of the line. Your results may differ because of your pipe layeout.

If you use a boiler for heat, many of them with the use of an indirect water tank, would end up being less expensive to install and maintain than a tankless. The better tanks lose only about 1/4-degree per hour in standby.

It should also be noted that the Metlund and TACO systems stop pumping once they sense a 5 deg rise in temperature (ambient). The results in some amount of water still being wasted waiting for the hot water you desire. We believe Metlund d'mand systems chose this form of operation to extend the life of the pump. Having the ability to adjust the temperature setpoint accurately is essential inorder to optimize resources and comfort. Any system which lacks this feature is almost guaranteed to under pump (still wait) or over pump (wait for cold). RedyTemp hot water circulators temperature can be adjusted down to 0.5 deg increments.

For homes which already have a working closed loop system, homeowners who want to save energy and minimize their circulators pump operations or turn their system into a on-demand system we are now selling the TLC-X2-115 Thermo Logic Controller by itself shown here http://www.redytemp.com/tanklesshotwatercirculator.php.

It includes;

Control Box with adjustable temperature
Digital Timer w/20 settings per 24hr period
Detachable power cord (identical to standard computer power cords)
Relocate-able stainelss steel temperatue probe ("L" in above link)
(with 1/2" compression fitting, wires pre-crimped with quick connects to allow for easy extension wires and strategic relocation of probe near last hot water load on the loop. Thus minimizing operations and lowering demand on the water heater.)

Installation is as simple as connecting existing pumps power positive/negative/ground wires to the control box. Install 1/2" compressioned temperature probe, and mounting the control box using it's keyhole cutouts on the back of the box to a wall.

As long as the pump to be controlled does not pull more than 2 amps, and is not a variable speed pump, it should work. To order the control box, you currently need to phone in the order.